Matt Reach

Core Animation 与 UIView.frame

2017-09-14

作者 : 田顺建 。

引言

在做一次关于Core Animation的分享时,老大提出了一个很是尖锐的问题——如果让layer保持动画后的状态,那么layer对应的view的响应区域是否是动画后view展示在屏幕上的区域?带着这个问题,开启Core Animation与view.frame的讨论。

Core Animation 与 view.frame

首先,先来看一下Core Animation对view.frame的影响。对于CALayer,有以下属性会对view的frame产生影响,包括:anchorPoint、position、transform。

首先,通过以下代码,创建了一个红色button,并且在打印出动画前button和button.layer的frame,为了便于观察动画前后的位置,还创建了一个只有黑色边框的view

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UIButton *moveButton = [UIButton buttonWithType:UIButtonTypeCustom];
moveButton.backgroundColor = [UIColor redColor];
moveButton.frame = CGRectMake(50, 100, 40, 40);
[moveButton addTarget:self action:@selector(moveButtonClicked) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:moveButton];
self.moveButton = moveButton;

NSLog(@"动画之前 frame: %@",NSStringFromCGRect(self.moveButton.frame));
NSLog(@"动画之前 layer frame: %@",NSStringFromCGRect(self.moveButton.layer.frame));

UIView *bgView = [[UIView alloc] initWithFrame:CGRectMake(48, 98, 44, 44)];
bgView.backgroundColor = [UIColor clearColor];
bgView.layer.borderColor = [UIColor blackColor].CGColor;
bgView.layer.borderWidth = 1;
[self.view addSubview:bgView];

在动画结束之后,再次打印button和button.layer的frame:

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-(void)animationDidStop:(CAAnimation *)anim finished:(BOOL)flag{
NSLog(@"动画之后 frame: %@",NSStringFromCGRect(self.moveButton.frame));
}
NSLog(@"动画之后 layer frame: %@",NSStringFromCGRect(self.moveButton.layer.frame));

anchorPoint

看一下使用Core Animation对anchorPoint做动画:

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CABasicAnimation *positionAnimation = [CABasicAnimation animationWithKeyPath:@"anchorPoint.x"];
positionAnimation.fromValue = @0.5;
positionAnimation.toValue = @1;
positionAnimation.duration = 1;
positionAnimation.repeatCount = 1;
positionAnimation.delegate = self;
positionAnimation.fillMode = kCAFillModeForwards;
positionAnimation.removedOnCompletion = NO;
[self.moveButton.layer addAnimation:positionAnimation forKey:@"anchorPoint"];

动画后如下:

此时,看一下console中的关于frame的输出信息:

使用Core Animation对anchorPoint做动画前后,虽然在屏幕上看起来,button的位置发生了变化,但是从console的输出可以看出,button和button.layer的frame是没有变化的。

并且,此时点击红色button左半边,是不会触发button的响应事件的,而点击黑框中的区域,即红色button动画前的区域,是可以触发button的响应事件。

position

接下来看一下对layer的position做CA动画,frame的变化。

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CABasicAnimation *positionAnimation = [CABasicAnimation animationWithKeyPath:@"position.x"];
positionAnimation.fromValue = @70;
positionAnimation.toValue = @250;
positionAnimation.duration = 1;
positionAnimation.repeatCount = 1;
positionAnimation.delegate = self;
positionAnimation.fillMode = kCAFillModeForwards;
positionAnimation.removedOnCompletion = NO;
[self.moveButton.layer addAnimation:positionAnimation forKey:@"Position"];

动画后如下:

console中的关于frame的输出信息:

红色button的frame依然没有变化,并且,只有点击黑框中的区域,才能触发button的响应事件。

transform

transform可以对layer实现旋转rotation、缩放scale、平移transition等动画。

对于rotation

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CABasicAnimation *rotationAnimation = [CABasicAnimation animationWithKeyPath:@"transform.rotation.z"];
rotationAnimation.fromValue = @0;
rotationAnimation.toValue = @(M_PI/4);
rotationAnimation.duration = 1;
rotationAnimation.repeatCount = 1;
rotationAnimation.delegate = self;
rotationAnimation.fillMode = kCAFillModeForwards;
rotationAnimation.removedOnCompletion = NO;
[self.moveButton.layer addAnimation:rotationAnimation forKey:@"Rotation"];

对于scale

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CABasicAnimation *scaleAnimation = [CABasicAnimation animationWithKeyPath:@"transform.scale"];
scaleAnimation.fromValue = @0.5;
scaleAnimation.toValue = @3;
scaleAnimation.duration = 1;
scaleAnimation.repeatCount = 1;
scaleAnimation.removedOnCompletion = NO;
scaleAnimation.fillMode = kCAFillModeForwards;
scaleAnimation.delegate = self;
[self.moveButton.layer addAnimation:scaleAnimation forKey:@"Scale"];

对于transition

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CABasicAnimation *rotationXAnimation1 = [CABasicAnimation animationWithKeyPath:@"transform.translation.x"];
rotationXAnimation1.fromValue = @(0);
rotationXAnimation1.toValue = @200;
rotationXAnimation1.duration = 1;
rotationXAnimation1.removedOnCompletion = NO;
rotationXAnimation1.fillMode = kCAFillModeForwards;
rotationXAnimation1.repeatCount = 1;
rotationXAnimation1.delegate = self;
[self.moveButton.layer addAnimation:rotationXAnimation1 forKey:@"Translation"]

并且上述三种动画之后,console中的输出均为下图所示:

红色button的frame依然没有变化,并且,只有点击黑框中的区域,才能触发button的响应事件。

结论

由此得出结论,Core Animation是作用在CALayer上的,不论CALayer在动画结束前后,是否保持动画后的状态,都不会改变view和view.layer的frame以及view的事件响应区域,即view和view.layer的frame均不会改变,并且view的事件响应区域也没有改变

Tags: issues
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